Long time ago it was decided that group name from class should be removed
https://www.drupal.org/node/2065827 →
In my opinion it's strange or weird that in case the field group is not collapsible and has no 'Extra CSS classes' then the field group div has no classes at all.
Plus when updating my very old site to the newest version (1.1 -> 1.5), hell broke loose.
Closed: won't fix
1.0
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